Sheathing over Wall detail (Brick Shelf & Exterior Insulation)
Hi GBA Community,
I’m trying to work in some exterior insulation sheathing for my new home that I am building (Northeast Zone 5). My architect didn’t spec any so it seems like I am on my own. My framers are asking me to decide how thick I want to go with it. I had planned on using the Polyiso from Johns Manville because this would get me the most R-Value by the inch. With 2″x6″ exterior walls with planned Rockwool or Cellulose, I cannot get anything greater than what the code requires for R-Value, hence my plan to bring in some exterior insulation.
My question is around where the sheathing meets the foundation. I have a 12″ foundation wall with a 4″ brick shelf. I understand that you want the 2″x6″ sill plate to line up with the outside of the wall allowing the plywood sheathing to overlap the foundation wall. Unfortunately with my brickshelf, I’m already limited with space and I need to maintain the recommend 1″ air gap. Question is, from what I know you normally want the plywood sheathing to overlap the foundation wall. In my case, can the plates be moved in where the plywood and insulated sheathing be flush with the wall instead? Then I’d have to cantilever the brick at least another 5/8″ to get that 1″ gap. How big of a deal is this gap anyway?
Any other suggestions/approaches would be helpful. I may be going about this all wrong. I’m in this position because the foundation contractor only formed a 4″ brick shelf, should have increased that another 1″ to give me some more breathing room. I through together an example of what I was seeing in my head, but any advice would be huge.
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